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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
364849
2Even Fibonacci numbers
301601
3Largest prime factor
220354
4Largest palindrome product
200665
5Smallest multiple
214210
6Sum square difference
215861
710001st prime
184883
8Largest product in a series
164182
9Special Pythagorean triplet
162027
10Summation of primes
148406
11Largest product in a grid
111707
12Highly divisible triangular number
100968
13Large sum
107559
14Longest Collatz sequence
105449
15Lattice paths
87772
16Power digit sum
110277
17Number letter counts
72551
18Maximum path sum I
71144
19Counting Sundays
65623
20Factorial digit sum
100708
21Amicable numbers
70571
22Names scores
65878
23Non-abundant sums
49539
24Lexicographic permutations
57028
251000-digit Fibonacci number
77120
26Reciprocal cycles
40614
27Quadratic primes
42838
28Number spiral diagonals
56908
29Distinct powers
51343
30Digit fifth powers
54620
31Coin sums
40359
32Pandigital products
34748
33Digit canceling fractions
35887
34Digit factorials
47683
35Circular primes
43594
36Double-base palindromes
46391
37Truncatable primes
36899
38Pandigital multiples
31328
39Integer right triangles
36257
40Champernowne's constant
40627
41Pandigital prime
33971
42Coded triangle numbers
38939
43Sub-string divisibility
28840
44Pentagon numbers
27802
45Triangular, pentagonal, and hexagonal
36937
46Goldbach's other conjecture
29579
47Distinct primes factors
28430
48Self powers
61578
49Prime permutations
28133
50Consecutive prime sum
30317